The present invention relates in general to portable, engine-powered, hand tools, and more specifically, to a clearing saw with a changeable circular saw blade. Such tools include an engine, a housing and a rotatable drive shaft connected to a rotating cutting tool, such as a circular saw blade, that is releasably fastened to the end of the shaft. A locking pin is movable in an axial direction into a hole in the shaft, or a part attached to the shaft, to fix the shaft in a non-rotating mode in relation to the housing to facilitate installation and removal of the cutting tool. In portable, engine-powered, hand tools like clearing saws, the cutting tool is fastened to the shaft, extending from a gear box, for example, bu a nut screwed on to a threaded end of the shaft. In order to facilitate the changing of the cutting tool, the shaft must be stopped from rotating relative to the housing to make it possible to rotatably release or fasten the nut. The shaft is stopped from rotation by the locking pin that is moved into a position to interfere with shaft rotation wherein the shaft is blocked from rotating in relation to the gearbox. It is desirable to keep the locking pin in this locking position even if the machine is turned up side down or otherwise moved around so as to make it easier to change the cutting tool by unscrewing the nut.
There are different known methods to keep the locking pin in a locking position wherein the shaft is not able to rotate. These prior art methods utilize mechanical latching solutions including multiple parts. Since clearing saws work in very rough conditions, the mechanical latching solutions do not always work properly because of the dirt, dust wood particles, and other debris that can interfere with the mechanical latches during use. Another well known solution is to use a locking pin mounted in a hole in the housing and being under influence of a biasing spring that acts in an axial direction on the locking pin to hold it or bias it in an unlocking position. The locking pin is movable in an axial direction to a locking position and is mounted on the housing in such a manner that it will not fall out of the hole. The locking pin can be pushed into a locking position by the user by pressing a finger against the pin with a force stronger than the biasing spring. The user must keep his finger on the pin to keep the shaft locked, otherwise the pin will return to its normal, spring-biased, non-locking position. This solution might include a releasable stop device that keeps the pin in the locking position, however, such a mechanism would make the tool heavier and more complex.
The purpose of the present invention is to make a locking assembly of the aforementioned type that eliminates the above-described prior art problems. A tool according to the subject invention would also be easier to handle, would work better in hostile environments, and would produce a tool at lower cost than the prior art solutions described.